Computer navigation and total knee arthroplasty

The Usefulness of a Simplified Navigation-Based Instrumentation for a Novice Surgeon in Primary Total Knee Arthroplasty: A Retrospective Analysis of a Randomized Controlled Trial

Background

A novel simplified navigation-based instrumentation system has been developed. It simplifies the existing navigation system and facilitates convenient bone cutting by positioning the tracker on an existing cutting block without additional pin fixation. This study aimed to compare the outcomes of this newly developed simplified navigation-based instrumentation system in primary total knee arthroplasty (TKA) performed by a novice surgeon with those of conventional surgical techniques.

Methods

From January 2020 to July 2020, 67 knees that underwent primary TKA using the ExactechGPS TKA Plus (group A) were compared to 68 knees that underwent primary TKA using a conventional technique (group B). All patients had a minimum follow-up of 24 months. The operative details such as tourniquet time were investigated. Postoperative hip-knee-ankle (HKA) angle and component position angles in the coronal and sagittal planes (α, β, γ, and δ angles) were evaluated. The outlier rates were compared between the groups as those lying outside ± 3°. Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, the Western Ontario and McMaster Universities Osteoarthritis Index for pain and function, and range of motion were compared.

Results

There was no statistically significant difference in average tourniquet time between the groups (74.3 vs. 70.3 minutes, p = 0.061). Outlier rates for HKA angle (7.5% vs. 23.5%, p = 0.010) and β angle (1.5% vs. 22.1%, p < 0.001) in group A were significantly lower than those in group B. There were no significant differences in clinical outcomes between the groups.

Conclusions

Primary TKA performed by a novice surgeon using a simplified navigation-based instrumentation system did not significantly increase the operation time, and more accurate lower extremity mechanical alignment and tibial component alignment in the coronal plane could be obtained.

The learning curve associated with imageless navigation in total knee arthroplasty

INTRODUCTION

Computer-assisted navigation systems (CAS) are increasingly being integrated into total knee arthroplasty (TKA) procedures, but perceptions of associated learning curve and increased operative time continue to curtail uptake. Newer-generation navigational systems aim to streamline integration into surgical workflow to mitigate increases in operative time. Here, we assess the impact of a novel imageless CAS on operative time for TKA.

METHODS

A retrospective analysis of prospectively collected data of a cohort of patients undergoing primary unilateral TKA with one of three surgeons between October 2019 and March 2020 was conducted. Consecutive cases using a novel imageless CAS were included in analysis. For each surgeon, average operative time was recorded and compared in sequential five-case cohorts to average operative time for the same procedure performed conventionally using a two-tailed t test.

RESULTS

Average conventional operative times were 95.9 ± 15.0, 86.6 ± 13.7, and 116.9 ± 25.1 min for the three surgeons. Initial CAS-assisted operative times increased to 107.0 ± 9.8 (p = 0.07) and 102.4 ± 13.2 (p = 0.06) min for Surgeons 1 and 2 and decreased to 113.2 ± 9.8 min (p = 0.52) for Surgeon 3. Most recent CAS-assisted operative times were 94.8 ± 13.9 (p = 0.88), 88.7 ± 15.3 (p = 0.84), and 104.8 ± 13.2 (p = 0.12) min as compared to pre-CAS. Absolute differences for the most recent navigated procedures ranged from 12.1 min faster to 2.0 min slower.

CONCLUSION

The learning curve for TKA navigation may be as few as 10 cases, and any associated increases in operative time may be transient and non-significant. Moreover, navigation may ultimately speed operative time, perhaps as the result of enhanced intraoperative assessment of alignment.

[Research progress on comparison of the application effects between personal specific instrumentation and computer-assisted navigation surgery in total knee arthroplasty]

OBJECTIVE

To compare the application effects between personal specific instrumentation (PSI) and computer-assisted navigation surgery (CAS) in total knee arthroplasty (TKA).

METHODS

The literature comparing the application effects of PSI and CAS in TKA in recent years was widely consulted, and the difference between PSI-TKA and CAS-TKA in operation time, lower limb alignment, blood loss, and knee function were compared.

RESULTS

Compared to CAS-TKA, PSI-TKA simplifies operation procedures and shortens operation time but probably has worse lower limb alignment. It is still controversial in comparison of perioperative blood loss and knee function between two techniques.

CONCLUSION

PSI-TKA and CAS-TKA both have advantages and disadvantages, and their differences need to be confirmed by further high-quality clinical trial.

Use of Navigation-Enhanced Instrumentation to Mitigate Surgical Outliers During Total Knee Arthroplasty

Computer-assisted orthopedic surgery improves mechanical alignment and the accuracy of surgical cuts in the context of total knee arthroplasty (TKA). A simplified, navigation-enhanced instrumentation system was assessed to determine whether the same effects could be achieved with a less intrusive system. Two cohorts of surgeons (experienced and trainees) performed a series of TKA cuts using models with and without navigation-enhanced instrumentation. The accuracy of each system was determined via the rate of outliers, measured as any cut that deviated from the planned cut by more than 2° or 2 mm. The effect of experience level was limited, with only the outlier rate for tibial varus or valgus measurement showing a significant difference between user groups with conventional instrumentation (P=.004). The use of navigation-enhanced instrumentation significantly reduced the total outlier rate compared with conventional instrumentation from 35% to 4% for experienced users (P<.001) and from 34% to 10% for trainees (P<.001). These results suggest that navigation-enhanced instrumentation is a viable alternative to conventional instrumentation to reduce outlier rates and improve cut accuracy. This trial also showed that additional experience may not correlate with improved surgical accuracy. Outliers may not reflect individual surgical ability as much as limitations of the instrumentation or other unidentified factors. [Orthopedics. 2021;44(1):54-57.].

Robotic Surgery in Total Joint Arthroplasty: A Survey of the AAHKS Membership to Understand the Utilization, Motivations, and Perceptions of Total Joint Surgeons

BACKGROUND

In the past decade, the popularity of robot arm assistance in total joint arthroplasty has outpaced the reporting of long-term data. This study aimed to understand the motivations for use and perceptions of the technology among total joint surgeons.

METHODS

An online survey was distributed to the membership of the American Association of Hip and Knee Surgeons. The questions were asked for respondent's motivations for utilization of the technology, perceptions regarding outcomes and training, and personal characteristics that may have influenced responses.

RESULTS

Increased precision was the primary reason for users (73.1%) to utilize robot arm assistance in total joint procedures. Nonusers were just as likely to consider adopting the technology because of increase precision and marketing (P = .590). Nonclinical reasons such as marketing, administrative pressure, and peer pressure were primary motivators for 19.7% of users of the technology. Respondents regardless of financial interest and use of the technology felt that robot arm assistance increased operative time (76.5%) and was not more cost-effective than traditional methods (78.7%). Most American Association of Hip and Knee Surgeons members felt that 20-40 surgical cases were needed to become competent with the technique (54.1%). A unique finding of this study is that a larger proportion of orthopedic surgeons considered themselves "innovators" or "early adopters," based on Roger's diffusion of innovations, than was expected for the general population.

CONCLUSION

This study demonstrates that the decision to adopt robot arm assistance in total joint arthroplasty is multifactorial and may have a significant contribution from nonclinical factors and inherent surgeon characteristics. Continued evaluation of surgeon perceptions will be valuable as new evidence emerges regarding long-term outcomes.

Appropriateness of the Use of Navigation System in Total Knee Arthroplasty

Backgroud

The aim of this study was to evaluate the difference between the planned and verified actual values in total knee arthroplasty (TKA) performed using a navigation system.

Methods

Sixty patients who underwent primary TKA for knee pain from March 2018 to July 2018 were included in this study. All patients underwent TKA using the latest version of a computer navigation system (Kick ver. 2.6). All TKA procedures were performed by the same surgeon. The appropriateness of the use of navigation system in each of the several steps during the operation was investigated. Implant size was assessed using a preoperative template and after registration of landmarks with the navigation system. Intraoperative measurement was conducted using a femoral sizing implant apparatus. The difference between the planned value based on the navigation system and the actual cutting value was investigated. Intraoperatively confirmed hip-knee-ankle angle was also compared to the angle measured at postoperative 3 months.

Results

The average time spent on the registration process was 242 seconds (range, 205-345 seconds). Intraoperative femoral component size tended to be smaller than the size recommended by the navigation system. A significant difference between the planned distal femoral cutting level (9.08 ± 0.40 mm) and the verified actual cutting level (9.87 ± 1.39 mm) was identified (p < 0.05). The difference between the planned lateral and medial tibial resection levels (10.12 ± 0.34 mm and 4.47 ± 2.17 mm, respectively) and the verified actual lateral and medial tibial resection levels (9.07 ± 1.45 mm and 3.48 ± 2.00 mm, respectively) was statistically significant. Distal femoral cutting angle in sagittal plane was significantly different but femoral and tibial cutting angles showed no significant difference between the planned and verified values. At full extension, the average coronal alignment of the implant recorded after insertion of the actual implant using the navigation system was 0.23° ± 0.51° varus and showed no significant difference from the alignment measured at postoperative 3 months (0.45° ± 0.58°).

Conclusions

When performing navigation-assisted TKA, surgeons should aware that frequent errors can occur on the femoral cutting level, tibial cutting level, and implant sizing despite its reported advantage in defining the mechanical limb axis.

Outcomes of Computer-Assisted Surgery Compared with Conventional Instrumentation in 19,221 Total Knee Arthroplasties: Results After a Mean of 4.5 Years of Follow-Up

BACKGROUND

Studies have shown improved alignment in association with the use of computer-assisted surgery (CAS) as compared with conventional instrumentation during total knee arthroplasty (TKA) but have failed to show a consistent clinical benefit. The aim of the present study was to compare the revision rates and functional outcomes following TKA performed with either CAS or conventional instrumentation. Recognizing that selection bias may arise from the preferential use of CAS in difficult or complex cases, the implant survival data and postoperative functional scores were analyzed with reference to whether the surgeon routinely performed TKA with use of CAS or conventional instrumentation.

METHODS

Revision rates and functional data in terms of the Oxford Knee Score (OKS) at 6 months, 5 years, and 10 years were obtained from the New Zealand Joint Registry (NZJR) for 19,221 TKAs performed from 2006 to 2018.These data were analyzed by comparing 2 cohorts of patients: those managed by high-volume surgeons who routinely used CAS ("routine CAS" surgeons) and those managed by high-volume surgeons who routinely used conventional instrumentation ("routine conventional" surgeons). The mean duration of follow-up was 4.5 years (range, 0 to 12 years).

RESULTS

The revision rate per 100 component-years was 0.437 for the "routine CAS" surgeons, compared with 0.440 for the "routine conventional" surgeons (p = 0.724). For patients <65 years of age, the revision rate per 100 component-years was equivalent for the "routine CAS" and "routine conventional" surgeons (0.585 compared with 0.508; p = 0.524). The OKS scores were similar at 6 months (38.88 compared with 38.52; p = 0.172), 5 years (42.26 compared with 41.77; p = 0.206), and 10 years (41.59 compared with 41.74; p = 0.893) when comparing the 2 cohorts. Surgeons who had performed >50 TKAs with use of CAS took 10 minutes longer on average than those who used conventional instrumentation (92 compared with 82 minutes; p = 0.012).

CONCLUSIONS

The present study demonstrated no difference in survivorship or functional outcome scores to support using CAS for TKA. Experienced surgeons using CAS had longer operative durations than comparable surgeons using conventional instrumentation.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Computer-Assisted Technologies in Arthroplasty: Navigating Your Way Today

Computer-assisted technologies that are used in arthroplasty include navigation, image-derived instrumentation (IDI), and robotics. Computer-assisted navigation improves accuracy and allows for real-time assessment of component positioning and soft-tissue tension. It is not clear whether the implementation of these technologies improves the clinical outcome of surgery. High cost and time demands have prevented the global implementation of computer-assisted technologies.

An umbrella review comparing computer-assisted and conventional total joint arthroplasty: quality assessment and summary of evidence

Background

Systematic reviews (SRs) of computer-assisted (CA) total knee arthroplasty (TKA) and total hip arthroplasty (THA) report conflicting evidence on its superiority over conventional surgery. Little is known about the quality of these SRs; variability in their methodological quality may be a contributing factor. We evaluated the methodological quality of all published SRs to date, summarized and examined the consistency of the evidence generated by these SRs.

Methods

We searched four databases through December 31, 2018. A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR 2) was applied to assess the methodological quality. Evidence from included meta-analyses on functional, radiological and patient-safety outcomes was summarized. The corrected covered area was calculated to assess the overlap between SRs in including the primary studies.

Results

Based on AMSTAR 2, confidence was critically low in 39 of the 42 included SRs and low in 3 SRs. Low rating was mainly due to failure in developing a review protocol (90.5%); providing a list of excluded studies (81%); accounting for risk of bias when discussing the results (67%); using a comprehensive search strategy (50%); and investigating publication bias (50%). Despite inconsistency between SR findings comparing functional, radiological and patient safety outcomes for CA and conventional procedures, most TKA meta-analyses favored CA TKA, whereas most THA meta-analyses showed no difference. Moderate overlap was observed among TKA SRs and high overlap among THA SRs.

Conclusions

Despite conclusions of meta-analyses favoring CA arthroplasty, decision makers adopting this technology should be aware of the low confidence in the results of the included SRs. To improve confidence in future SRs, journals should consider using a methodological assessment tool to evaluate the SRs prior to making a publication decision.

Trends in computer navigation and robotic assistance for total knee arthroplasty in the United States: an analysis of patient and hospital factors

Background

Computer navigation and robotic assistance technologies are used to improve the accuracy of component positioning in total knee arthroplasty (TKA), with the goal of improving function and optimizing implant longevity. The purpose of this study was to analyze trends in the use of technology-assisted TKA, identify factors associated with the use of these technologies, and describe potential drivers of cost.

Methods

The Nationwide Inpatient Sample database was used to identify patients who underwent TKA using conventional instrumentation, computer navigation, and robot-assisted techniques between 2005 and 2014. Variables analyzed include patient demographics, hospital and payer types, and hospital charges. Descriptive statistics were used to describe trends. Univariate and multivariate analyses were performed to identify differences between conventional and technology-assisted groups.

Results

Our analysis identified 6,060,901 patients who underwent TKA from 2005 to 2014, of which 273,922 (4.5%) used computer navigation and 24,084 (0.4%) used robotic assistance. The proportion of technology-assisted TKAs steadily increased over the study period, from 1.2% in 2005 to 7.0% in 2014. Computer navigation increased in use from 1.2% in 2005 to 6.3% in 2014. Computer navigation was more likely to be used in the Western United States, whereas robot-assisted TKAs were more likely to be performed in the Northeast. Increased hospital charges were associated with the use of technology assistance ($53,740.1 vs $47,639.2).

Conclusions

The use of computer navigation and robot-assisted TKA steadily increased over the study period, accounting for 7.0% of TKAs performed in the United States in 2014. Marked regional differences in the use of these technologies were identified. The use of these technologies was associated with increased hospital charges.

Computer-Assisted Compared with Conventional Total Knee Replacement: A Multicenter Parallel-Group Randomized Controlled Trial

BACKGROUND

We previously reported the short-term radiographic and functional results of a randomized controlled trial (RCT) comparing computer-assisted and conventionally performed total knee replacement. We currently report the 2-year clinical results from this trial.

METHODS

One hundred and ninety patients were randomly allocated to undergo either computer-assisted or conventional total knee replacement. One hundred and seventy-two patients were available for clinical evaluation at 2 years, and 167 (97%) of those answered all patient-reported outcome measures (PROMs), including the Knee Injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Society Score (KSS), visual analog scale (VAS), and EuroQol-5 Dimensions (EQ-5D). Patients and clinical evaluators were blinded to the method of surgery. Surgical outcome was assessed using the Outcome Measures in Rheumatology-Osteoarthritis Research Society International (OMERACT-OARSI) criteria to calculate responder rates, divided into high responders, moderate responders, and nonresponders.

RESULTS

The computer-assisted group had significantly more improvement than the conventional group in the mean scores for 2 subscales of the KOOS (7.4 for symptoms [p = 0.02] and 16.2 for sport and recreation [p < 0.01]) and in 1 subscale of the WOMAC (8.8 for stiffness [p = 0.03]).The computer-assisted group also had significantly more high responders (82.8%) than the conventional group (68.8%; p = 0.03) at 2 years, with the number needed to treat determined to be 8.

CONCLUSIONS

In this study, the use of computer navigation provided better pain relief and restored better function than the use of the conventional surgical technique at 2 years after total knee replacement.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Increased precision of coronal plane outcomes in robotic-assisted total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

Inaccuracy of component alignment in total knee arthroplasty adversely impacts outcomes. Robotic systems improve translation of pre-operative planning to intra-operative steps, theoretically resulting in greater accuracy and precision. In this study we systematically review literature data of alignment outcomes and apply meta-analysis methods to assess whether robotic-assisted knee arthroplasty provides superior outcomes when compared to conventional knee prostheses.

METHODS

A PRISMA compliant search comparing alignment outcomes in robotic vs conventional knee arthroplasty was performed. Primary outcome measures were; number of three degree outliers and mean deviation from a neutral post-operative mechanical axis.

RESULTS

In total, from five studies reporting upon 402 knees, a post-operative mechanical axis malalignment of >3° occurred in 1/181 (0.006%) of robotic knees, and 42/159 (26.4%) of conventional knees with a meta-analysis odds ratio of 0.04 (95% CI 0.01-0.14), p < 0.00001 favouring robotic-assisted instrumentation. Meta-analysis also demonstrated weighted mean differences of post-operative mechanical axis alignment to be significantly more accurate in the robotic knee group: mean difference -0.63 (95% CI: -1.18,-0.08), z = 2.25, p = 0.02. Sensitivity analysis with inclusion of only Level 1 studies showed similar findings.

CONCLUSIONS

This systematic review and meta-analysis demonstrates clear evidence of increased accuracy of alignment in robotic-assisted knee arthroplasty with specific regard to reconstituting a neutral mechanical axis and minimising number of outliers in the coronal plane. Further studies and long term data is required in order to conclude on survivorship and functional outcomes.

Articular surface mounted navigated total knee arthroplasty improves the reliability of component alignment

PURPOSE

The primary aim was to compare the early knee-specific functional outcome after articular surface mounted (ASM) navigation with non-navigated TKA. The secondary aims were to compare general physical and mental health improvement, patient satisfaction, and reliability of component alignment in the sagittal and coronal planes between ASM navigated TKA with that of non-navigated TKA.

METHODS

Prospective functional outcome and radiographic data were collect for 123 patients undergoing ASM navigation and 172 patients undergoing non-navigated TKA by a high volume single surgeon. Pre-operative and one-year Oxford knee score (OKS) and short form (SF-) 12 scores were collected. Patient satisfaction was also assessed at one year. Implant position was assessed on post-operative radiographs (alpha, beta, gamma, and sigma angles) by a blinded observer.

RESULTS

There was no significant difference for improvement in OKS, SF-12 physical or mental components, or satisfaction between the groups one year following surgery. The non-navigation group was significantly more likely to have outliers (greater than 3 degrees) in femoral varus/valgus coronal alignment [odds ratio (OR) 4.5, 95% confidence interval (CI) 1.0-20.7, p = 0.049] and for posterior tibial slope (OR 8.3, 95% CI 1.1-65.0, p = 0.03).

CONCLUSIONS

ASM navigation significantly reduces the number of outliers for the femoral and tibial components when compared to conventional non-navigation alignment. However, the short-term functional outcome is not influenced by the surgical technique used. If the surgeon wants to reduce their number of outliers, then ASM navigation should be considered but the overall functional outcome in the short term is not influenced.

LEVEL OF EVIDENCE

III Therapeutic investigation, retrospective cohort study.

Computer Navigated Total Knee Arthroplasty: Rates of Adoption and Early Complications

BACKGROUND

When new technologies are introduced, it is important to evaluate the rate of adoption and outcomes compared with preexisting technology. The purpose of this study was to determine the adoption rate of computer-assisted navigation in total knee arthroplasty (TKA), to determine if the short-term complication rate changed over time with navigation, and to compare short-term complication rates of navigated and traditional TKA.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was used to identify 108,277 patients undergoing primary TKA between 2010 and 2014, of which 3573 cases (3.30%) were navigated. Rates of adoption of navigated TKA were determined. Differences in short-term complications by year were compared using propensity score matching.

RESULTS

Navigation utilization decreased from 4.96% in 2010 to 3.06% in 2014. Blood transfusion rates for the entire cohort decreased from 19% in 2011 to 6% in 2014, and was not decreased with navigation compared with traditional TKA in 2014 (P = .1309). Operative time was not increased by navigation, and average 94.2 minutes. There were no significant differences in all-cause complications, reoperation rate, unplanned readmission, or length of stay for any year.

CONCLUSIONS

There was a 38.3% decrease in TKA navigation utilization from 2010-2014. Blood transfusion rates decreased 68% over the 5-year study, and were not decreased with navigation in 2014. Navigation was not found to increase operative time. There were no significant differences in short-term complications, readmission rate, or length of stay between navigated and traditional TKA.

Have the Causes of Revision for Total and Unicompartmental Knee Arthroplasties Changed During the Past Two Decades?

BACKGROUND

Revisions after knee arthroplasty are expected to increase, and the epidemiology of failure mechanisms is changing as new implants, technology, and surgical techniques evolve.

QUESTIONS/PURPOSES

(1) Was there improvement in survival for TKA and unicompartmental knee arthroplasty (UKA) when comparing two consecutive 11-year periods with similar followups in a national registry? (2) Were there changes in the causes of revision during the two times? (3) Could the changes in revision causes be attributed to patient or implant characteristics?

METHODS

A total of 60,623 TKAs (2426 revisions) and 7648 UKAs (725 revisions) were selected from the Norwegian Arthroplasty Register and analyzed based on year of primary surgery: 1994 to 2004 (Period 1) and 2005 to 2015 (Period 2). TKAs had median followup of 3.5 years in Period 1 and 4.2 years in Period 2. Median followup for UKAs was 2.7 years in Period 1 and 4.6 years in Period 2. Of the patients included in the registry, 99.6% were accounted for at the time of analysis, whereas 0.4% had moved abroad. We used Kaplan-Meier analyses and log-rank test to investigate changes in survival. Relative risk of revision in Period 2 relative to Period 1 was calculated for each registered revision cause in a Cox regression model adjusted for age, sex, diagnosis, fixation, and patella resurfacing.

RESULTS

For TKAs, the 10-year Kaplan-Meier survival free from revision improved from Period 1 to Period 2 from 91% (95% CI, 90%-92%) to 94% (95% CI, 94%-95%; p < 0.001). Revisions resulting from aseptic loosening of the femoral component, polyethylene wear/breakage, patellar dislocation, and unexplained pain decreased, whereas revisions resulting from early infection increased. Patients in Period 2 were younger and more often men compared with patients in Period 1. A higher risk of revision was found for male sex (relative risk [RR], 1.1; 95% CI, 1.0-1.2; p = 0.048) and age younger than 65 years (RR, 1.7; 95% CI, 1.6-1.9; p < 0.001). With UKAs, the 10-year survival free from revision was 80% (95% CI, 76%-84%) in Period 1 and 81% (95% CI, 79%-83%; p = 0.261) in Period 2. Revisions resulting from tibial aseptic loosening, polyethylene wear/breakage, and periprosthetic fractures decreased, but there were more revisions resulting from progression of osteoarthritis. In Period 2, there were more men and the average age was younger than for patients in Period 1. For UKAs, age younger than 65 years had a higher risk of revision (RR, 1.7; 95% CI, 1.5-2.0; p < 0.001), whereas sex did not affect the risk of revision.

CONCLUSIONS

We found an improvement in survival free from revision for TKA in the last period, but no similar improvement for UKA, and the survivorship for UKAs remains rather dramatically lower than that observed for TKAs. The decision to perform a UKA should be made with the explicit awareness that its survivorship is substantially inferior to that of TKA; any perceived advantages of UKA should be balanced against this issue of its decreased durability.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Similar migration in computer-assisted and conventional total knee arthroplasty

Background and purpose - Computer-assisted surgery (CAS) in total knee arthroplasty (TKA) has been used in recent years in the hope of improving the alignment and positioning of the implant, thereby achieving a better functional outcome and durability. However, the role of computer navigation in TKA is still under debate. We used radiostereometric analysis (RSA) in a randomized controlled trial (RCT) to determine whether there are any differences in migration of the tibial component between CAS- and conventionally (CONV-) operated TKA. Patients and methods - 54 patients (CAS, n = 26; CONV, n = 28) with a mean age of 67 (56-78) years and with osteoarthritis or arthritic disease of the knee were recruited from 4 hospitals during the period 2009-2011. To estimate the mechanical stability of the tibial component, the patients were examined with RSA up to 24 months after operation. The following parameters representing tibial component micromotion were measured: 3-D vector of the prosthetic marker that moved the most, representing the magnitude of migration (maximum total point motion, MTPM); the largest negative value for y-translation (subsidence); the largest positive y-translation (lift-off); and prosthetic rotations. The precision of the RSA measurements was evaluated and migration in the 2 groups was compared. Results - Both groups had most migration within the first 3 months, but there was no statistically significant difference in the magnitude of the migration between the CAS group and the CONV group. From 3 to 24 months, the MTPM (in mm) was 0.058 and 0.103 (p = 0.1) for the CAS and CON groups, respectively, and the subsidence (in mm) was 0.005 and 0.011 (p = 0.3). Interpretation - Mean MTPM, subsidence, lift-off, and rotational movement of tibial trays were similar in CAS- and CONV-operated knees.

Long-term functional outcomes and knee alignment of computer-assisted navigated total knee arthroplasty

INTRODUCTION

This retrospective study examined the relationship between the mechanical axis throughout a functional arc of motion and functional outcome scores in patients undergoing computer-assisted navigation-based total knee arthroplasty (CAN-TKA) at 6-year follow-up.

MATERIALS AND METHODS

The Stryker eNact Precision Knee Navigation System was utilized to obtain pre- and postoperative alignment measurements throughout the functional arc of motion. Patients were contacted via telephone and asked to complete the Short Form-12 and Western Ontario and McMaster Universities, which have been demonstrated to be reliable, valid, and sensitive assessment tools in this patient population. Statistical analysis was performed to determine the correlation between arc alignment and patient-reported functional outcome measures.

RESULTS

A total of 47 patients at a mean of 76.1 (±6.3)-month follow-up and mean age of 65.9 (±7.9) years were surveyed. No correlation was found between the postoperative alignment or degree of intraoperative correction and the functional outcome scores. In a planned subgroup analysis of patients with a mean functional arc alignment greater than 3° from neutral, mean intraoperative degree of correction correlated with decreasing physical function (Spearman's ρ = 0.772, p = 0.04) and mean postoperative arc alignment positively correlated with increasing stiffness (ρ = 0.798, p = 0.03).

CONCLUSION

This study suggests that patients undergoing CAN-TKA with mean functional arc range of motion greater than 3° may be at increased risk for suboptimal patient-reported functional outcomes. This study also illustrates the ability of CAN-TKA to measure the varus or valgus alignment of the knee throughout the entire range of motion.

Survivorship and relative risk of revision in computer-navigated versus conventional total knee replacement at 8-year follow-up

Background and purpose - The long-term effects of computer-assisted surgery in total knee replacement (CAS) compared to conventionally operated knee replacement (CON) are still not clear. We compared survivorship and relative risk of revision in CAS and CON based on data from the Norwegian Arthroplasty Register. Patients and methods - We assessed primary total knee replacements without patellar resurfacing reported to the Norwegian Arthroplasty Register from 2005 through 2014. The 5 most used implants and the 3 most common navigation systems were included. The groups (CAS, n = 3,665; CON, n = 20,019) were compared using a Cox regression analysis adjusted for age, sex, ASA category, prosthesis brand, fixation method, previous surgery, and diagnosis with the risk of revision for any reason as endpoint. Secondary outcomes were reasons for revision and effects of prosthesis brand, fixation method, age (± 65 years), and hospital volume. Results - Prosthesis survival and risk of revision were similar for CAS and CON. CAS had significantly fewer revisions due to malalignment. Otherwise, no statistically significant difference was found between the groups in analyses of secondary outcomes. Mean operating time was 13 minutes longer in CAS. Interpretation - At 8 years of follow-up, CAS and CON had similar rates of overall revision, but CAS had fewer revisions due to malalignment. According to our findings, the benefits of CAS at medium-term follow-up are limited. Further research may identify subgroups that benefit from CAS, and it should also emphasize patient-reported outcomes.

Current state of computer navigation and robotics in unicompartmental and total knee arthroplasty: a systematic review with meta-analysis

Recently, there is a growing interest in surgical variables that are intraoperatively controlled by orthopaedic surgeons, including lower leg alignment, component positioning and soft tissues balancing. Since more tight control over these factors is associated with improved outcomes of unicompartmental knee arthroplasty and total knee arthroplasty (TKA), several computer navigation and robotic-assisted systems have been developed. Although mechanical axis accuracy and component positioning have been shown to improve with computer navigation, no superiority in functional outcomes has yet been shown. This could be explained by the fact that many differences exist between the number and type of surgical variables these systems control. Most systems control lower leg alignment and component positioning, while some in addition control soft tissue balancing. Finally, robotic-assisted systems have the additional advantage of improving surgical precision. A systematic search in PubMed, Embase and Cochrane Library resulted in 40 comparative studies and three registries on computer navigation reporting outcomes of 474,197 patients, and 21 basic science and clinical studies on robotic-assisted knee arthroplasty. Twenty-eight of these comparative computer navigation studies reported Knee Society Total scores in 3504 patients. Stratifying by type of surgical variables, no significant differences were noted in outcomes between surgery with computer-navigated TKA controlling for alignment and component positioning versus conventional TKA (p = 0.63). However, significantly better outcomes were noted following computer-navigated TKA that also controlled for soft tissue balancing versus conventional TKA (mean difference 4.84, 95 % Confidence Interval 1.61, 8.07, p = 0.003). A literature review of robotic systems showed that these systems can, similarly to computer navigation, reliably improve lower leg alignment, component positioning and soft tissues balancing. Furthermore, two studies comparing robotic-assisted with computer-navigated surgery reported superiority of robotic-assisted surgery in controlling these factors. Manually controlling all these surgical variables can be difficult for the orthopaedic surgeon. Findings in this study suggest that computer navigation or robotic assistance may help managing these multiple variables and could improve outcomes. Future studies assessing the role of soft tissue balancing in knee arthroplasty and long-term follow-up studies assessing the role of computer-navigated and robotic-assisted knee arthroplasty are needed.